Studies of the Protein Binding of Testosterone in Plasma in Disorders of Thyroid Function: Effect of Therapy

ABSTRACT Results of studies of the percentage binding of testosterone in plasma and the fractional distribution of 3H-testosterone among the plasma proteins are given in hyperthyroidism and hypothyroidism before and after return to the euthyroid state. The percentage binding of testosterone was significantly increased and decreased in hyperthyroidism and hypothyroidism, respectively. The in vitro testosterone saturation curves showed a remarkable increase in testosterone binding capacity of plasma in hyperthyroidism with a decrease in hypothyroidism. The fractional distribution of 3H-testosterone among the plasma proteins revealed an increase and decrease in the radioactivity associated with the β-globulins (peak II) in hyperthyroidism and hypothyroidism, respectively. These measurements returned to or toward normal following return to the euthyroid state. This study demonstrates that the state of thyroid function has a significant effect on the binding of testosterone in plasma and provides an explanatio...